Support # as an external type URL

Closes #2855
Closes #2853

Author: Gerrit0

Diff for: CHANGELOG.md

@@ -7,6 +7,7 @@ title: Changelog
 ### Features
 
 -   The `--favicon` option may now be given a link starting with `https?://` instead of a path, #2851.
+-   TypeDoc now supports specifying `#` as the link in `externalSymbolLinkMappings` to indicate the type should not be linked to, #2853.
 
 ### Bug Fixes
 

Diff for: site/development/third-party-symbols.md

@@ -65,7 +65,10 @@ Plugins can add support for linking to third party sites by calling
 
 If the given symbol is unknown, or does not appear in the documentation site,
 the resolver may return `undefined` and no link will be rendered unless provided
-by another resolver.
+by another resolver. The string `"#"` may also be returned to indicate that
+TypeDoc should mark the symbol as externally resolved, but not produce a link
+to it. This can be useful if you want to keep the link for usage in VSCode,
+but not include it in the documentation.
 
 The following plugin will resolve a few types from React to links on the
 official React documentation site.

Diff for: site/options/comments.md

@@ -267,3 +267,22 @@ the special `global` package reserved for global types.
     }
 }
 ```
+
+The string `"#"` may also be specified to indicate to TypeDoc that the type should be marked as resolved
+but no link should be created.
+
+```json
+// typedoc.json
+{
+    "externalSymbolLinkMappings": {
+        // used by {@link !Promise}
+        "global": {
+            "Promise": "#"
+        },
+        // used by type Foo = Promise<string>
+        "typescript": {
+            "Promise": "#"
+        }
+    }
+}
+```

Diff for: src/lib/output/formatter.tsx

@@ -515,15 +515,21 @@ const typeBuilder: TypeVisitor<
                 );
             }
         } else if (type.externalUrl) {
-            name = simpleElement(
-                <a
-                    href={type.externalUrl}
-                    class="tsd-signature-type external"
-                    target="_blank"
-                >
-                    {type.name}
-                </a>,
-            );
+            if (type.externalUrl === "#") {
+                name = simpleElement(
+                    <span class="tsd-signature-type external">{type.name}</span>,
+                );
+            } else {
+                name = simpleElement(
+                    <a
+                        href={type.externalUrl}
+                        class="tsd-signature-type external"
+                        target="_blank"
+                    >
+                        {type.name}
+                    </a>,
+                );
+            }
         } else if (type.refersToTypeParameter) {
             name = simpleElement(
                 <span class="tsd-signature-type tsd-kind-type-parameter">